The proposed study aims to develop a novel cognitive-behavioral therapy (CBT) protocol aimed at reducing high- risk behaviors, as well as improving resiliency and addressing important developmental issues in youth with bipolar disorder (BPD) who are transitioning to adulthood. BPD is one of the most disabling psychiatric conditions, associated with significant morbidity, poor functional outcomes, and elevated rates of high-risk behaviors and substance use disorders. Recently, promising CBT interventions have been developed as adjuncts to medication in the treatment of BPD. Yet there are no CBT interventions specifically aimed at reducing high-risk behaviors among young adults with BPD and at improving their resiliency to cope with the common life stressors and developmental transitions that are important destabilizing factors during this period. Therefore, the goal of this exploratory/development application is to develop and pilot test a 14-week adjunctive group CBT intervention for young adults (ages 18-24) with BPD that includes modules on 1) facilitating a collaborative care model of treatment for BPD and enhancing self-efficacy in managing the disorder;2) reducing high-risk behaviors including suicidality, substance use and abuse, risky sexual practices, gambling, and/or dangerous driving;and 3) enhancing psychosocial functioning and resilience by improving age-appropriate autonomy, problem-solving, social support, and stress-buffering skills. CBT strategies with demonstrated efficacy will be integrated with interventions consistent with the transtheoretical model of behavior change to target high-risk behaviors and functional impairments in an individualized manner. During the first stage of treatment development (12 months), we will develop and refine the treatment manual, and will openly implement the intervention with a group of 6-8 young adults to evaluate its feasibility and acceptability. In stage 2, we will pilot test the efficacy of the intervention by conducting a controlled study of 48 young adults with BPD (or bipolar spectrum disorder). Study participants will be randomized either to the 14-week adjunctive group CBT intervention in addition to treatment-as-usual (n=24), or to a 14-week control condition in which they receive treatment-as-usual only (n=24). Participants randomized to treatment-as-usual will be eligible to receive the intervention after the 14-week study. Participants who complete treatment will be assessed at post-treatment and at 6-month follow-up to evaluate maintenance of treatment gains. The proposed study will provide important information about the feasibility, efficacy, and effect size of this innovative intervention for young adults with BPD. Thus, in offering ways to augment pharmacotherapy in mitigating the severity and impact of this devastating disorder in youth, the proposed study will be of major clinical, public health, and scientific importance.